Hydrological budgets and surface energy balance of seven subbasins of the Mackenzie River from the ECMWF model

The liquid and frozen hydrological budgets and the surface energy budget fr om seven subbasins of the Mackenzie River are analyzed using hourly integra ls from the operational European Centre for Medium-Range Forecasts model fr om September 1996 to August 1998. The model budgets give estimates of preci pitation (rainfall and snowfall), surface evaporation (of water and snow), runoff, and melt terms in the spring. On a basin scale and monthly timescal e, the model precipitation correlates well with observations but has a 40% positive bias. On an annual basis, evaporation has a 60% positive bias. Alt hough the annual runoff for the Mackenzie as a whole is close to the annual stream flow, this condition is not true for the subbasins. In the liquid w ater budget, nudging of soil water compensates for basin errors in runoff. The model snow budget is not closed because each new snow analysis depends heavily on climatological means. The surface energy balance on the basin sc ale also is analyzed. Although the model gradients of net radiation probabl y are realistic, the model evaporation bias means that sensible heat flux i s negatively biased, especially in spring.